Experimental and theoretical study on wax deposition and the application on a heat insulated crude oil pipeline in Northeast China

Sun, Dongxu; Zhu, Zuoliang; Hu, Zhiyong; Wu, Ming

doi:10.2516/ogst/2019064

Cited by 10 publications

(5 citation statements)

References 22 publications

(25 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The numerical simulations were performed under steady-state conditions using CFD software. Sun et al [14] performed an experimental and theoretical study of wax deposition behaviors on a heat-insulated waxy crude oil pipeline in Northeast China. The effects of flow rate and ambient temperature on the thickness and wax content of the deposition layer were investigated.…”

Section: Introductionmentioning

confidence: 99%

Mathematical Modeling of Wax Deposition in Field-Scale Crude Oil Pipeline Systems

Ochieng

Kinyanjui

Abonyo

et al. 2022

Journal of Applied Mathematics

View full text Add to dashboard Cite

The formation of solid wax crystals, which interlock and form a gel-like layer on the inner wall of the crude oil pipeline, influences the transportation of waxy crude oil. The deposited layer grows continuously and hardens during the oil transportation, reducing the effective inside diameter of the crude oil pipeline and the flow rate. In extreme cases, the deposited layer may block the crude oil pipeline leading to a loss of production and capital investment. In this paper, wax deposition from multiphase flow in field-scale oil pipeline transport systems has been studied. The novelty of this work is to develop a mathematical model that incorporates water-in-oil emulsions, wax precipitation kinetics, molecular diffusion, and shear dispersion to enable accurate predictions of both the wax deposit growth rate and aging of the deposit. The coupled nonlinear partial differential equations governing the flow are discretized in time by a second-order semi-implicit time discretization scheme based on the Adams-Bashforth and Crank-Nicolson methods, which completely decouples the computation of the governing equations. The resulting temporal schemes are discretized in space by the bivariate spectral collocation method based on Chebyshev-Gauss-Lobatto grid points and simulated in MATLAB software to obtain the profiles of the flow variables. The simulation results are presented in graphical and in tabular forms and discussed. This study found that the deposit thickness is directly proportional to the Reynolds number and inversely proportional to the mass Grashof number, Schmidt number, and Weber number. Deposit aging is rampant during the early stages of wax deposition, after which it stabilizes at a specific value as time elapses. A deposition model to predict the wax deposit thickness and aging is proposed in this study. The findings of this study will help in making informed decisions on the planning of pigging operations, thermal insulation, and other remediation techniques to be applied in controlling wax deposition in field-scale crude oil pipeline systems.

show abstract

Section: Introductionmentioning

confidence: 99%

Mathematical Modeling of Wax Deposition in Field-Scale Crude Oil Pipeline Systems

Ochieng

Kinyanjui

Abonyo

et al. 2022

Journal of Applied Mathematics

View full text Add to dashboard Cite

show abstract

“…For this, many scholars have conducted numerous studies on wax deposition in the multiphase pipelines, and they have a relatively comprehensive understanding of its influencing factors and deposition characteristics. However, with the deepening of the research, the wax deposition mechanism is still needed to be refreshed and improved. ,, Based on recent studies on wax deposition and some classic literatures, this paper summarized the new wax deposition mechanisms proposed by researchers in recent years and several typical experimental devices for studying wax deposition, and the wax deposition characteristics and prediction models in single- and two-phase flow systems and the wax–hydrate coupling deposition in oil–gas–water flow systems have been determined, to provide reference for researchers engaged in single-phase and multiphase flow assurance.…”

Section: Introductionmentioning

confidence: 99%

Wax and Wax–Hydrate Deposition Characteristics in Single-, Two-, and Three-Phase Pipelines: A Review

Liu

Wang

et al. 2020

Energy Fuels

View full text Add to dashboard Cite

In the oil pipeline transportation system, wax deposition will reduce the effective circulation area, weaken the overall pipeline transportation capacity, and even block the pipeline, which seriously threatens the safety of the pipeline flows. In the actual production of oil fields and the transportation of oil products, except for the single-phase waxy crude oil, under most conditions, operations are performed using multiphase mixed transportation, so it is necessary to determine the wax deposition characteristics in those pipeline systems. In this Review, three new wax deposition mechanisms proposed in recent years and several typical experimental devices were summarized, the wax deposition in oil–water and oil–gas flow systems and the wax–hydrate coupling deposition in oil–gas–water flow system flows were concluded; the mathematical models were also categorized based on the three flow systems. Meanwhile, it highlighted the fact that, in the two-phase flow, because of the complexity of the flow pattern and the presence of the second interface on the wax deposition process, independent theoretical research on the mechanism of wax deposition is particularly necessary; based on this, a more-accurate wax deposition prediction model can also be developed. For the coupled deposition of wax-hydrate in the three-phase flow system, experimental instruments such as FBRM, PVM and molecular dynamics simulations could be used to study the distribution characteristics and interaction rules of wax crystals and hydrate particles from a microscopic perspective. On the other hand, the mechanism of wax crystal and hydrate coupling deposition by additives such as antiwax agents, hydrate inhibitors, antipolymerization agents, and pipeline transportation conditions can be investigated experimentally to better control the deposition process during pipeline operation and ensure the safe flow in the transportation system.

show abstract

“…In this case, according to the authors, no molecular diffusion mechanism could come into play because no concentration gradient would be established. Although recent publications still consider molecular diffusion as the dominant mechanism, , other authors are beginning to accept that molecular diffusion might not be the dominant wax deposition mechanism and that heat transfer may dominate the early stages of the deposit formation, with molecular diffusion contributing at later stages. − Also, it has been considered that the effect of cooling rate and the non-Newtonian behavior of the wax solution and deposit gel need to be considered. ,,− …”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Study of Wax Deposition in a Laboratory-Scale Pipe Section under Well-Controlled Conditions

et al. 2020

View full text Add to dashboard Cite

Detailed local and averaged measurements of wax deposition in an annular pipe section were conducted and combined with a comprehensive simulation model. The objective of the study was to contribute to the understanding of the fundamental mechanisms responsible for wax deposition on surfaces. To this end, a laboratory-scale annular deposition section was designed to offer well-defined boundary and initial conditions for the deposition experiments. The test section allowed visual access to the deposit formation process and was equipped with a traversing, fine-gage temperature probe and a port for sampling of the deposit. The measurements encompassed the time evolution of the axial distribution of deposit thickness, radial temperature profiles, and deposit composition. Measurements were made for deposition times, ranging from 5 min to 7 h, for laminar flow conditions. A special model solution was employed, formed by a single-molecule solvent and paraffins with a narrow carbon number distribution. This simple model solution facilitated the simulations and comparison with experiments. The simulation model solved the equations governing conservation of mass, linear momentum, energy, and chemical species, coupled with a multisolid thermodynamic model for predicting solid−liquid equilibrium. The enthalpy-porosity approach was employed to model the deposition process, with the deposit treated as a porous medium with variable porosity depending on the solution solid fraction. An excellent agreement was obtained between the measured and predicted deposit thicknesses. Enrichment of the deposit with heavier carbon molecules with time and Reynolds number was measured, characterizing the aging process. The simulations also predicted the same trends, but deviations from the experiments were found for longer deposition times. The measured and predicted temperature profiles agreed in the region close to the deposition wall. As the deposit interface was approached, the simulations predicted slightly warmer temperatures. The time evolution of the simulated species concentration profiles displayed depletion of the solvent and enrichment of the heavy components in the deposit. An increased concentration of the heavy paraffins in the liquid region close to the deposit interface was predicted. This finding indicates that, possibly, a local elevated value of wax appearance temperature prevailed, justifying the presence of crystals flowing over the deposit surface visualized in the experiments. For the test conditions investigated, the combined observations of experimental results and simulations indicate that molecular diffusion at the deposit interface is not the dominant deposition mechanism. Rather, the observations indicate that liquid−solid phase transition governed by heat transfer, coupled to diffusive and convective fluxes of the chemical species, seems to determine the deposit formation.

show abstract

Experimental and theoretical study on wax deposition and the application on a heat insulated crude oil pipeline in Northeast China

Cited by 10 publications

References 22 publications

Mathematical Modeling of Wax Deposition in Field-Scale Crude Oil Pipeline Systems

Mathematical Modeling of Wax Deposition in Field-Scale Crude Oil Pipeline Systems

Wax and Wax–Hydrate Deposition Characteristics in Single-, Two-, and Three-Phase Pipelines: A Review

Experimental and Numerical Study of Wax Deposition in a Laboratory-Scale Pipe Section under Well-Controlled Conditions

Contact Info

Product

Resources

About